Steroid injections are often used to treat localized musculoskeletal or neurogenic pain. In practice, the corticosteroid is often mixed with a local anesthetic and injected into a patient's joint, tendon sheath, or adjacent to a painful ligament or inflamed nerve. The corticosteroid acts over several days to manage inflammation and pain, while the local anesthetic works immediately, but only temporarily. If the injection is properly placed, the local anesthetic will instantly numb the patient's pain, and the practitioner can be reasonably assured that the corticosteroid will be injected in the proper area to effectively manage pain. A successful local treatment of musculoskeletal or neurogenic pain improves the patient's function and decreases the need for systemic medications and even surgery, in some cases.
In the current state of the art, the preparation of such an injection requires a practitioner to gather a variety of supplies including the corticosteroid and anesthetic, a syringe and needles, and local anesthetic, among other things. The length of time it takes to prepare the injection can depend on the availability and accessibility of the supplies and the efficiency and organization of the medical office and staff. Lack of even one item, whether it is misplaced, out of stock, outdated, contaminated or in another area, can extend preparation time. The entire process can be very time consuming and can be a limiting factor in the number of such treatments a practitioner can administer in one day.
One example of a device that attempts to address these problems is disclosed in U.S. Pat. No. 7,100,771 B2 to Massengale et al. The Massengale patent relates to a pain management kit containing the primary medical supplies for performing a continuous nerve block procedure. The kit comprises sterile field supplies, local anesthetic supplies and continuous nerve block supplies in a single, sterile container. Inside the container, the supplies are organized within a series of compartmentalized trays which hold each of the included supplies. The particular anesthetic drug is omitted from the kit.
One disadvantage of this kit, however, is that the desired infusion drug and several other necessary supplies, such as nerve simulator and an infusion pump, are not contained within the kit. Therefore, the practitioner would still have to gather additional supplies, in addition to the kit, in order to perform the nerve block procedure. If any of these supplies are out of stock, misplaced, in another room, or in use by another practitioner, the procedure will be delayed.
Another factor which greatly affects the time to prepare an injection for pain management as described at the outset is that the practitioner must manually measure and mix the corticosteroid and anesthetic from separate vials immediately before use. This has several significant disadvantages. First, this can again add considerable time to the overall length of the procedure, depending on the dexterity and experience of the doctor. Even if all of the materials are within the practitioner's reach, he/she still must take the time to draw separate volumes of both the corticosteroid and anesthetic. Second, certain safety risks are associated with manually preparing the injection for each administration. Not only can human error play a role when manually measuring the two solutions, but also sterility is an issue when the vials of corticosteroid and anesthetic are reused to prepare several injections often by different practitioners at the same site. Third, the vials of corticosteroid and anesthetic have a limited shelf-life once they punctured, so if they are not completely used within the allotted time, they must be discarded, which can be costly. In fact, a practitioner that would not normally administer enough of these injections to avoid wasting opened vials of the pre-mixed corticosteroid or anesthetic may choose not to perform these types of procedures altogether.
However, in the current state of the art, corticosteroid premixed with local anesthetic is not readily commercially available. Many steroid preparations are suspensions of particles, which settle to the bottom of their glass vials within minutes of no motion. These particles can stick firmly to the glass vial and require vigorous shaking to re-suspend.
Furthermore, mixing syringes currently known in the field have the disadvantage of introducing air into the mixed solution. For example, in U.S. Pat. No. 7,101,354 to Thorne, Jr. et al., a small amount of air is contained in the chambers 120, 130 to aid in the creation of a negative pressure across the valved stopper 110. Any air within the chamber must be removed before injecting the mixed solution into a patient, which again can lengthen the time of a procedure.
Prior art mixing syringes also have the disadvantage of requiring the puncturing or rupturing of a membrane, diaphragm or other material separating the two injection solutions. When this rupturing or puncturing occurs, minute fragments of the separating material may be mixed into the injection. These materials may have an adverse effect when injected into the human body with the injection mixture.
What is desired, therefore, is a pre-packaged, sterile pain management kit which contains all of the instruments and supplies necessary to treat localized musculoskeletal or neurogenic pain. It is further desired to have a syringe containing pre-measured volumes of corticosteroid and local anesthetic in separate compartments that can be quickly mixed into a homogeneous chemical mixture immediately prior to use, without rupturing or puncturing of a separating material and without introducing air into the mixture.